The Duke and Duchess of Cambridge attend the ceremonial welcome ceremonyLeon Neal/AFP

She greeted President Tony Tan and his wife Mary at the Royal Garden Hotel and told them "I've been looking forward to getting out of the house, that's for sure."

Kate is 12 weeks pregnant and has been receiving treatment for severe morning sickness, which also plagued her first pregnancy. This was her first public appearance since the announcement of her pregnancy.

The Duke and Duchess of Cambridge pose for a photo with the President of Singapore Tony Tan Keng Yam and his wife Mary Chee Bee Kiang at the Royal Garden Hotel on the first of a four-day state visit to BritainAnthony Devlin/PoolKate Middleton and Mary Tan depart the Royal Garden Hotel in LondonBen A Pruchnie/Getty ImagesThe skirt of Kate Middleton's silver Alexander McQueen coat is caught by the windChris Jackson/Getty ImagesKate Middleton wears a silver Alexander McQueen coat and a Jane Taylor hat as she and Prince William prepare to welcome the President of SingaporeChris Jackson/Getty ImagesKate takes her seat in a State Carriage for the procession to Buckingham Palace as part of the ceremonial welcome ceremony for Singapore's PresidentLeon Neal/AFP

She plans to attend the Wildlife Photographer of the Year awards gala at the National History Museum tonight (21 October).

The Queen and Prince Philip welcomed the president of Singapore and his wife to Britain at the start of their four-day state visit.

The Queen talks with Mary Tan, wife of Singapore's President Tony Tan Keng Yam, as Prime Minister David Cameron, Foreign Secretary Philip Hammond and Home Secretary Theresa May stand by during the ceremonial welcome ceremonyLeon Neal/AFPPrime Minister David Cameron bows to the Queen at HorseguardsChris Jackson/Getty ImagesThe Queen and the Duke of Edinburgh smile as they prepare to welcome the President of SingaporeChris Jackson/Getty ImagesMembers of The Royal Horse Guards are seen prior to the arrival of the President of Singapore Tony Tan Keng Yam at the Royal Garden HotelChris Jackson/Getty ImagesThe Queen is pictured during the carriage procession to the palaceLeon Neal/AFPThe President of Singapore Tony Tan inspects a Guard of HonourToby Melville/Reuters